A. Field of Invention
This invention relates generally to measuring the quantity of liquid in a storage container and more particularly to gauge the quantity of propellant in a tank.
B. Description of the Related Art
It is well known in the art to measure the amount of liquid in a storage tank. The general concept of measuring the electromagnetic eigenmodes of a tank as a method to gauge the quantity of liquid in a propellant tank dates back to 1966, when Lockheed Missiles and Space Company first tested the technique as a level sensor in tanks partially filled with RP-1, liquid hydrogen, and liquid oxygen.
While known measurement methods perform well for their intended purpose, there are limitations. One limitation is that the configuration of the liquid in the tank at low or partial gravity is uncertain. Another limitation is that the configuration of a liquid, which is sloshing or splashing within the tank at any gravity, is uncertain. Another limitation is the complexity of converting a tank radio frequency (RF) spectrum into a propellant quantity reading. Another limitation is accurately predicting the field modes of the tank.
Therefore, what is needed is a highly accurate RF measurement method and apparatus to gauge the amount of propellant in a tank.